Hey everybody,
I want to implement a mass-conserving Kumar-Booker cavitation algorithm to Comsol. Therefore I'd like to use a PDE in coefficient form (c) in order to describe the modified Reynolds-equation according to Kumar & Booker.
I have to solve for 2 variables: p and teta:
- In the pressure region where p>0: p unknown, teta=1 known
- In the cavitation region where p<=0: p=0 known, teta unknown
I'm using a switch variable (if(p>0,1,0)) in the diffusion coefficient, so I can eliminate the Poiseulle-term in the cavitation region. Furthermore I have two Dirichlet boundary conditions. One sets p to 0 on both boundaries, the other one sets teta to 1 at the inlet boundary. Next to that I have a compelemtary conditions which sets teta to 1 if p>0.
When I try to solve this, it says there is a singularity in my matrix as p has too many degrees of freedom (empty columns in the matrix).
Maybe one of you can help me with this.
Thanks in advance!
I want to implement a mass-conserving Kumar-Booker cavitation algorithm to Comsol. Therefore I'd like to use a PDE in coefficient form (c) in order to describe the modified Reynolds-equation according to Kumar & Booker.
I have to solve for 2 variables: p and teta:
- In the pressure region where p>0: p unknown, teta=1 known
- In the cavitation region where p<=0: p=0 known, teta unknown
I'm using a switch variable (if(p>0,1,0)) in the diffusion coefficient, so I can eliminate the Poiseulle-term in the cavitation region. Furthermore I have two Dirichlet boundary conditions. One sets p to 0 on both boundaries, the other one sets teta to 1 at the inlet boundary. Next to that I have a compelemtary conditions which sets teta to 1 if p>0.
When I try to solve this, it says there is a singularity in my matrix as p has too many degrees of freedom (empty columns in the matrix).
Maybe one of you can help me with this.
Thanks in advance!